Conventionally, as a facility for sending and receiving information between various electronic apparatuses introduced into a home, for example, such as a television receiver, a video recorder, a DVD apparatus, a personal computer and the like, a system has been proposed for establishing in the home a network to connect those electronic apparatuses to each other by using various interfaces.
However, if the network through which those electronic apparatuses are connected to each other is established in the home, for example, this home network and an external network are connected to each other through the Internet and the like. Consequently, information reproduced or reconstructed in the home, for example, a picture information reproduced by a DVD apparatus can be instantly distributed to many and unspecified persons. This results in a problem that the copyright of its content cannot be sufficiently protected.
As this counter-plan, a copy protection system is proposed for inserting, for example, a memory card recording a control information, into each electronic apparatus, and limiting a copy of information received or reproduced by the electronic apparatus, and thereby preventing the information from being limitlessly escaped, and consequently protecting the copyright. In this method, a common encryption key (hereafter, suitably referred to as “Group Key”) is assigned to an electronic apparatus connected to a network in a home. The group key is recorded on the memory card. The information is encrypted using the group key that is recorded on the memory card. Therefore, the information cannot be reconstructed if the group key is not known even in a case that the information is externally escaped. Consequently the copyright is protected.
For example, a content outputted from an information receiver (hereafter, suitably referred to as “STB: Set Top Box”) is encrypted using a group key in a memory card inserted into the STB, and this encrypted content is decoded and displayed using the group key in a memory card inserted into a television monitor. Thus, even if the encrypted content is escaped into an external network, the content is never decoded unless there is the same group key as the group key used for the encryption.
However, the above-mentioned method involves the unit for inserting the memory cards into the respective electronic apparatuses, which results in the factor of an increase in a cost and restricts the miniaturization of the apparatus.
Furthermore, there is a further inconvenience in the above-mentioned method, i.e. only the electronic apparatuses to which the group key is assigned can reproduce the content information, while other electronic apparatuses to which the group key is not assigned cannot handle the content information whatever its kind or nature.